This invention relates generally to rotating disk data storage apparatus, and particularly to a disk drive for use with magnetooptical disks packaged in cartridge form with a sliding shutter. Still more particularly, the invention deals with improvements in such a magnetooptical disk drive designed to realize an appreciable reduction in the height or thickness dimension of the disk drive, by which is meant the dimension in a direction perpendicular to the plane of the magnetooptical disk loaded in the disk drive.
Magnetooptical disks with their erasable and rewritable capabilities have won extensive commercial acceptance in recent years as compact storage media of both computer data and user data. Such disks are available today in a variety of sizes, ranging from those as large as twelve inches in diameter to those as small as five and a quarter inches and three and a half inches in diameter. Usually, the disks are rotatably enveloped in generally flat, boxlike housings of plastics material complete with a sliding sheet-metal shutter to open and close access windows in the opposite sides of the housing.
The disk drive for use with such relatively small size disk cartridges has an entrance slot in its front face for the insertion of the disk cartridge in a horizontal plane. Mounted within the disk drive casing, a cartridge cradle receives the disk cartridge inserted in the entrance slot. The cartridge cradle has pivotally mounted thereon a shutter lever whereby, as heretofore constructed, the sliding shutter of the disk cartridge has been fully opened upon full insertion of the disk cartridge in the entrance slot. Then the cartridge cradle with the disk cartridge loaded therein is subsequently lowered to carry the disk cartridge down to a data transfer position in which the magnetooptical data storage disk is put to data transfer with an optical data transducer. This transducer utilizes a laser beam for reading, writing and erasing data on the magnetooptical disk.
Another standard component of the magnetooptical disk drive is an electromagnet assembly for generating a magnetic field which is necessary for biasing the disk during its data transfer with the optical data transducer. Normally, the electromagnet assembly is held in a standby position within the disk drive casing, in which position the electromagnet assembly overhangs the cartridge cradle being held in its raised position. After the loading of the disk cartridge in the cartridge cradle, the electromagnet assembly is lowered with the disk cartridge over a distance greater than the distance of descent of the disk cartridge, for applying a magnetic field to the disk through one of the access windows in the cartridge housing.
It is the above noted standby position of the electromagnet assembly over the cartridge cradle that has been an impediment to the reduction of the height or thickness dimension of the magnetooptical disk drive. However, this arrangement is per se desirable for the simplicity of the supporting and actuating mechanisms of the electromagnet assembly and for the reduction of the overall size of the disk drive, as the electromagnet assembly is required to move only up and down. An approach other than changing the standby position of the electromagnet assembly is therefore needed for the height reduction of the disk drive.